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Energetic materials, such as 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX), are known for their high energy output but low safety. The application of fluorine-containing materials in energetic materials can yield extraordinary results. This paper presents a gas-phase synthetic method for preparing perfluoroalkyl-functionalized graphene (PFG) and examines its desensitizing effect on HMX. PFG was synthesized under mild and safe conditions, and its structure was characterized. For comparison, alkyl-functionalized graphene (RG) was prepared using the same method. Seven composites of HMX with varying fluorine contents of PFG, as well as graphene, graphene oxide, amino-functionalized graphene, and RG were prepared by a solvent/nonsolvent method. HMX crystals grow as ellipsoids without sharp angles in PFG dispersions, which facilitate the reduction of mechanical sensitivity. Thermal analyses were conducted to determine the apparent activation energy and physical model of the thermal decomposition process. The results show that PFG inhibits the decomposition of HMX at low temperatures but accelerates its rapid decomposition rate at high temperatures. Mechanical sensitivity and thermal analysis studies suggest that 15%PFG is a promising coating agent to improve the safety of energetic materials. [ABSTRACT FROM AUTHOR]

In order to improve the energy efficiency of composite nano-metal materials, the energetic intermolecular complexes Si@PVDF/CL-20 with different silicon content (20%, 30% and 40%)were prepared by electrostatic spray method. The heat of combustion of PVDF/CL-20 composites with different ratios was obtained by bomb calorimeter. The morphology of PVDF/CL-20 composite was clarified by using SEM. The effect of Si content on the morphology of Si@PVDF/CL-20 composite particles was also analyzed. The thermal behavior of energetic compounds with different silicon content was studied by DSC-TG, and the kinetic paramters of thermal decomposition were calculated. The thermal analyses indicate that when the PVDF/ CL-20 mass ratio is 1-6, the heat of combustion reaches a maximum value, which can be used as the optimal ratio incoating of nano-Si powder. The SEM results show that when the silicon content is 30%, the composite particles (Si-30% ©PVDF/CL-20) exhibite the best sphericity. The DSC results show that when the silicon content is 20%, a runaway chemical reaction was likely occurred. The effect of Si powder on the decomposition of PVDF/CL-20 composite plays less significant role with the increase of content. The apparent activation energies of Si@PVDF/CL-20 composites calculated by Friedman method are 470. 6, 182.1, 91.7kJ/mol, respectively. The complex decomposition process of Si-20% @PVDF/CL-20 cannot be described by a single kinetic model, whereas those of Si-30% ©PVDF/CL-20 and Si-40% ©PVDF/CL-20 can be well described by a nuclea-tion and growth model. [ABSTRACT FROM AUTHOR]

Highlights: [•] Nonisothermal decomposition kinetics of RDX and its PBXs has been investigated. [•] The kinetic models are determined by both master plot and combined kinetic analysis methods. [•] The constant rate temperature profiles and isothermal curves are predicted by obtained kinetic triplets. [•] The storage safety parameters are simulated based on thermal explosion theory. [ABSTRACT FROM AUTHOR]

The crystal structure, thermal behavior, and decomposition kinetics of ε-CL-20, RS-ε-CL-20, α-CL-20, ε-CL-20/C4, and RS-ε-CL-20/C4 were investigated by nonisothermal FTIR, TG, and DSC techniques. It was found that the thermal decomposition of α-CL-20, ε-CL-20/C4, and RS-ε-CL-20/C4 could be considered as a two-step process and the initial step is partly controlled by crystal structure. However, the crystal structure could only affect the initial step of decomposition and the total heat release, and the heat release of RS-ε-CL-20 is the highest compared with α- and normal ε-CL-20. In addition, the activation energy of studied materials was calculated by Kissinger method and modified KAS method, which was compared with the results obtained by other researchers. It was indicated that the obtained activation energy of ε-CL-20 by Kissinger method is about 176.0 kJ mol, which is almost the same with the results from the literatures by STABIL and Noniso-TG methods. It was noticed that the crystal structure has significant effect on the initial activation energy distribution of CL-20, while in case of second stage (α = 0.30-0.85) this effect is relatively small, resulting in identical decomposition mechanism. Moreover, the kinetic compensation effects show that the studied materials could be divided into two groups, one including ε-CL-20, RS-ε-CL-20, α-CL-20, and ε-CL-20/C4 which decompose at solid state and another including ε-CL-20/Formex and RS-ε-CL-20/C4 which decompose at partial liquid state, resulting in different kinetic compensation effects. It reveals that the C4 base could affect the distribution of activation energy of ε-CL-20 and RS-ε-CL-20 in a totally different way. [ABSTRACT FROM AUTHOR]

Over the past 20 years, a number of scientists have conducted numerous fundamental investigations based on quantum chemistry theory into various mechanistic processes that seems to contribute to the sensitivity of energetic materials. A large number of theoretical methods that have been used to predict their mechanical and spark sensitivity are summarized in this article, in which the advantages and disadvantages of these methods, together with their scope of use are clarified. In addition, the theoretical models for thermal stability of explosives are briefly introduced as a supplement. It has been concluded that the current ability to predict sensitivity is merely based on a series of empirical rules, such as simple oxygen balance, molecular properties, and the ratios of C and H to oxygen for different classes of explosive compounds. These are valid only for organic classes of explosives, though some special models have been proposed for inorganic explosives, such as azides. An exact standard for sensitivity should be established experimentally by some new techniques for both energetic compounds and their mixtures. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Abstract: The thermal behavior and decomposition kinetics of C4-bonded PBXs based on some attractive cyclic nitramines were investigated by means of nonisothermal TG and DSC techniques. It has been shown that only a single decomposition process has been observed for RDX-C4 while an obvious two-step process for mixture of BCHMX-C4 CL-20-C4, and HMX-C4. The onset temperature of the exotherms were observed at 216.3, 238.7, 279.2 and 236.7°C with the peak temperatures of 235.1, 279.0, 231.2 and 233.7°C for RDX-C4, BCHMX-C4, HMX-C4 and CL-20-C4, respectively. Their corresponding exothermic decompostion processes were covered by energy changes of 1749, 1938, 1213 and 2639Jg−1, which are lower than that of their pure cyclic nitramines. It was also proved that C4 matrix has significant effect on the activation energy distribution of RDX, BCHMX and CL-20, whose initial autocatalysis effect was inhibited or weakened. With regard to HMX-C4, the activation energy of its initial step is much lower than that of the second step. [Copyright &y& Elsevier]

Thermal behavior and decomposition kinetics of Formex-bonded PBXs based on some attractive cyclic nitramines, such as 1,3,5-trinitro-1,3,5-triazinane (RDX) and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX). Actually, cis-1,3,4,6-tetranitrooctahy droimidazo-[4,5-d]imidazole (BCHMX) and 2,4,6,8,10,12-hexanitro-2,4,6,8,10, 12-hexaazaisowurtzitane (CL-20), was investigated by means of nonisothermal thermogravimetry (TG) and differential scanning calorimetry (DSC). It was found that the mass loss rate of PBXs involved in this research depends greatly on heating rate and the residue of the decomposition of these PBXs decreases with the heating rate. The onset of the exotherms was noticed at 215.4, 278.7, 231.2 and 233.7 °C with the peak maximum at 235.1, 279.0, 231.2 and 233.7 °C for RDX-Formex, HMX-Formex, CL-20-Formex, and BCHMX-Formex, respectively. Their corresponding exothermic changes were 1788, 1237, 691, and 1583 J g. It was also observed that the dependence on the heating rate for onset temperatures of HMX- and BCHMX-based PBXs was almost the same due to their similar molecular structure. In addition, based on nonisothermal TG data, the kinetic parameters for thermal decomposition of these PBXs were calculated by isoconversional methods. It was shown that the Formex base has great effects on the activation energy distribution of nitramines. It was further found that the kinetic compensation effects occurred during the thermal decomposition of nitramine-based PBXs, and they almost have the same compensation effects due to similar decomposition mechanism. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, several fundamental investigations published over the past decades with regard to the thermal analysis of polymer-based explosives (PBXs) have been briefly reviewed. A number of explosive fillers and polymer bases that were used as their main ingredients of PBXs are summarized herein. In addition, the calculation methods for their decomposition kinetics and thermal stability parameters are also introduced in detail. It was concluded that only PBXs based on HMX, RDX and TATB have been widely investigated, and that some other PBXs containing innovative fillers, such as CL-20, TNAZ, NTO and BCHMX are at the design stage. The isoconversional methods and model fitting procedures are usually used to analyze the discrete thermolysis processes of PBXs. In addition, their thermal stability parameters such as shelf life, explosion delay, critical temperature, thermostability threshold, 500-day cookoff temperature and approximate time to explosion could be calculated easily from the kinetic data. [Copyright &y& Elsevier]

Abstract: DNP, a nitramine, has been studied with regard to the kinetics and mechanism of thermal decomposition, using thermogravimetry (TG), differential thermal analysis (DTA), infrared (IR) spectroscopy, and differential scanning calorimetry (DSC). The IR spectra of DNP have also been recorded and the kinetics of thermolysis has been followed by non-isothermal TG. The activation energy of the solid-state process was determined using Flynn–Wall–Ozawa method. The actual reaction mechanism obeyed nucleation and growth model, Avramie Erofeev function (n =1) with integral form G(α)=−ln(1− α) (α =0.10–0.65). E a and A were determined to be 116.51kJ/mol and 1010.52 s−1. The T/Jump FT-IR analysis showed that CH2O, NO2, and NO are produced in larger amounts than CO2 and HCN. The cleavage of the N–N and C–N bond appears to be the primary step in the thermolysis of DNP. [Copyright &y& Elsevier]

• Composite propellants (CPs) containing insensitive high-energy qy-HMX have been prepared. • The qy-HMX-based CPs has 9.64% higher heat of explosion than HMX-based one. • The burn rate of CPs containing qy-HMX is 4.38 mm·s−1 at 3 MPa, 45.9% lower than that of corresponding HMX-based one. • The average particle size of the CCPs of qy-HMX-based CPs is 71.5% lower than that of HMX-based one. Two types of qy-HMX (insensitive HMX with improved energy density, numbered 1 and 2) have been used and studied as an ingredient of HTPB-based composite propellants (CPs), and the decomposition and combustion performances have been investigated. It has been shown that the main exothermic peak temperature of blank CPs containing 21 wt% of qy-HMX-1 is 258.9 °C, which is 4.7 °C higher than that of HMX-containing one, indicating improved thermostability. The corresponding heat of explosion for blank qy-HMX-2-based CPs was measured to be 5830 J∙g−1, which is 300 J∙g−1 higher than that of HMX-based one. Interestingly, the qy-HMX-2-based CPs has higher energy density than corresponding CL-20-based ones, but it has much lower burn rate under the same pressure, e.g. 4.38 mm∙s−1 at 3 MPa for the former vs. 9.03 mm∙s−1 for the latter. Under the effect of typical conventional catalysts such as nano-CuO and nano-Fe 2 O 3 , the qy-HMX-1-based CPs showed increased heat of explosion and higher burn rate. In addition, the particle sizes of condensed combustion products (CCPs) of CPs containing qy-HMX-2 are much smaller than that of HMX-based one, where the Al 4 C 3 was produced as its unique CCPs ingredient. [ABSTRACT FROM AUTHOR]

Highlights: [•] DHDNEBa was firstly synthesized by the process of metathesis reaction with a yield of 95.7%. [•] The most probable kinetic model function of the exothermic decomposition reaction was deduced. [•] ΔS ≠, ΔH ≠,ΔG ≠, T SADT and T b of DHDNEBa were investigated. [•] The thermal decomposition mechanism of DHDNEBa was studied by means of thermolysis/RSFTIR and TG–MS technologies. [ABSTRACT FROM AUTHOR]

• Tannic acid is used as an interfacial layer to tailor the monodisperse core-shell metal iodate-based MICs. • The modified MIC shows better long-term storage stability, enhanced thermal reactivity and energy release. • The improved combustion efficiency and burning rate have been demonstrated. As is known to all, the nano-aluminum (n-Al) of metastable intermixed composites (MICs) could be easily and slowly oxidized during long-term storage. Herein, a plant polyphenol, tannic acid (TA), has been used to coat n-Al as an interfacial layer to bind with metal iodates (Fe(IO 3) 3 , Cu(IO 3) 3 , Bi(IO 3) 3) forming MICs with tunable reactivity. The latter can be in-situ synthesized on the surface of TA to construct a core-shell n-Al@TA@M(IO 3) x MICs suing a facile, green and low-cost chemical way. Various characterization techniques are used to investigate the prepared these core-shell MICs, including scanning electron microscopy, transmission electron microscopy, X-ray energy dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, thermal analysis, bomb calorimetry and high-speed camera. The results showed that the obtained novel MICs were almost monodispersed and uniformly distributed. They have shown enhanced performances in terms of thermal reactivity, long-term storage, energy releases and combustion efficiency. For the thermal reactivity, the major exothermic peak temperature of n-Al@TA@M(IO 3) x can be reduced by about 16.9–48.6 °C by using TA as an interfacial layer in comparison with the mechanically mixed n-Al/M(IO 3) x. For the long-term storage stability, the energy loss of n-Al@TA@Fe(IO 3) 3 (11.0%) after three weeks aging is much less than that of n-Al/Fe(IO 3) 3 (35.3%). For the energy release, Fe(IO 3) 3 -based MICs can be increased to 24.1 kJ cm−3 (14.5% higher), whereas the Cu(IO 3) 3 -based MICs to 22.8 kJ cm−3 (19.4%) and Bi(IO 3) 3 -based MICs to 20.2 kJ cm−3 (3.1%). The burning rates of n-Al@TA@M(IO 3) x are 1.7 to 4.3 times higher than that of n-Al/M(IO 3) x , and the flame of n-Al@TA@M(IO 3) x is more homogeneous than that of n-Al/M(IO 3) x. [ABSTRACT FROM AUTHOR]